Radiant heater



NOV- 24, 1959 K. E. GANsKE ErAL 2,914,647

RADIANT HEATER Filed Aug. l2, 1957 INVENTORS KINGSTON E GAA/SKF ALBERTG. B/L L United States Patent O 2,914,647 RADIANT HEATER Kingston E.Ganske and Albert G. Bill, Columbus, Ind., assignors to ArvinIndustries, Inc., Columbus, Ind., a corporation of Indiana ApplicationAugust 12, 1957, Serial No. 677,479

11 Claims. (Cl. 219-34) SOuI'CC.

It is the general object of our invention to provide a radiant heaterwhich will overcome the difiiculties and disadvantages described aboveby providing safety with increased radiant heat output. Morespecifically, it is the .object of our invention to provide a radiantheater whose radiant heat output will be controlled in response tovariations in radiant heat reflected back to said heater.

In carrying out our invention in the preferred form, there is provided ahousing having an open forwardly presented face. A radiant heat sourceis mounted within `the housing and provided with a suitable retlectoradapted to reflect and direct the radiant heat outwardly from the heaterthrough the open face of the housing. Conveniently, the heater output iscontrolled by a thermostat operable for opening and closing the electriccircuit to the heat source. The thermostat is mounted at the front ofthe heater and insulated therefrom, with its forwardly presented face ofrelatively large extent sensing variations in the amount of radiantenergy reflected back tovward the heater. Thus, when an object placed infront of the heater reflects a predetermined amount of radiant energyback to the thermostat, the thermostat will be actuated to open thecircuit to the heat source to reduce the heat output and prevent burningthe object.

The accompanying drawings illustrate our invention. In such drawings: i

Fig. 1 is a front view of a radiant heater embodying our invention;

Fig. 2 is a vertical section taken on the line 2-2 of Fig. 1;

Fig. 3 is an enlarged horizontal section of the thermostat shown inFigs. 1 and 2;

Fig. 4 is a fragmental vertical section of a modified form of ourinvention;

Fig. 5 is a fragmental vertical section of another modiiied form of ourinvention; and

Fig. 6 is a Wiring diagram of a heater employing the heat responsivecontrol means shown in Fig. 5.

As illustrated in the drawings, our heater may be mounted in anysuitable housing 10 having an open forwardly presented face providedwith a protective grill 12. For purposes of convenience, the housing 10is tiltably supported at each of its ends on floor-engaging legs 14, andis provided with a handle for carrying the heater from one location toanother.

Disposed within the housing 10 is a pair of reflectors 16 extending thelength of the housing and having a generally parabolic cross-section.Desirably, the reflectors ICC 16 are formed from sheets of highlyreiiective metal for reflecting and directing radiant heat outwardlyfrom the heater through the open face of the housing 10. The reflectorsmay be mounted in the housing 10 in any convement manner.

Any suitable source of radiant heat, such as a Calrod heating element, aresistance winding on a ceramic core, or the like, may be employed inour heater. As shown, we employ a pair of radiant heating elements 23formed from coils of nichrome wire enclosed in glass tubes. Each of theheating elements 23 extends the length of one of the reflectors 16 andis mounted adjacent the focus thereof through blocks 19 of heat andelectrical insulating material.

The outputof the heating elements 23 is controlled by a radiantheat-responsive thermostat 30 desirably cen-` tered in the forwardlypresented face of the heater. The thermostat 30 is mounted on areflective cover 32 extending rearwardly over the adjacent forward edgesof the reflectors 16 toward the heating elements 23. The cover 32, whichis conveniently formed from the same reflective material as thereflectors 16, diverges outwardly from the heating elements 23 to shieldthe thermostat 30 from the direct and reflected radiation of theelements 23. A face plate 34 is mounted on the cover 32 by a roll seam35 which bindingly retains the plate 34 on the cover 32.

The thermostat 30 is mounted on the face plate 34 by bolts 36 receivedin a thermostat housing 38 and retained` in the plate 34. Preferably, aheat insulating spacer 41 is received on each of the bolts 36 to disposethe thermostat out of contact with the plate 34 and the cover 32 andthereby insulate the thermostat from any heat that may be conducted awayfrom the cover 32 and plate 34. Any suitable type of thermostat actuatedby reflected radiant heat may be used in our heater. One type of such athermostat is shown in Fig. 3, and comprises an outer metal housing 38having a generally cylindrical configuration with an inwardly directedlip 42 provided at one of its ends. A radially extending flange 44 isdisposed at the opposite end of the housing 38 which receives the bolts36 retaining the thermostat on the cover plate 34. Press fit within thehousing 38 is a base 46 formed of a heat resistant phenolic material andhaving an end plate 47 disposed substantially coplanar with the housingflange 44. A pair of inwardly directed arms 48 are formed integrallywith the side walls of the base 46 for supporting a pair of contacts 50connected in the electrical circuit of the heating elements 23 by wires52. Fixedly mounted on one end of a plunger 54 movable within the basebetween the ends of the arms 48 is a metal bridge 56 normally disposedagainst the contacts 50 for closing the electrical circuit to theheating elements 23. The plunger 54 is urged in this vnormallyclosed-circuit position by a leaf spring 57 secured to the bridge 56 andbearing against the base end plate 47.

Plunger movement for opening and closing the circuit to elements 23 isaccomplished by a slightly convex bimetal disc 60 comprising a forwardlypresented sheet of metal 62 having a relatively low coefficient ofexpansion and a rearwardly disposed sheet of metal 64 having arelatively high coefficient of expansion. The disc 60 is held in thethermostat 30 by having its margins bindingly received between theforward end of the base 46 and the housing lip 42, thereby permittingthe central portion of the disc to flex with a snap-action, or oil caneiect, in response to temperature variations in the disc. Preferably,the thermostat is disposed at the front of the heater in a position sothat the wires forming the grill 12 do not shield or block the disc 60from the heat reflected back toward the heater and thereby reduce itssensitivity. The sensitivity of the disc may be further increased byroughening and darkening the forwardly presented face of the disc metalsheet 62 to render it more absorptive to reected radiant heat.

In operation, the thermostat 30 is actuated to open the electricalcircuit to the heating elements 23 by radiant heat reflected back towardthe heater from an object or objects disposed in front of the heater.When the amount of reected heat is sufcient to actuate the thermostat,the metal 64 comprising the rearwardly presented face of the disc 60expands, flexing the disc to snap its center portion rearwardly andmoving the plunger 54 in a like direction. As the plunger movesrearwardly, the bridge 56 is displaced away from the contacts 50 openingthe electrical circuit to the heating elements 23 and reducing theiroutput. When the radiant heat reflected back to the disc 60 has beenreduced because of the reduced output of the heating elements 23 or bythe removal of the reflecting object, the metal sheet 64 cools andcontracts to its normally convex position, and the plunger 54 under theinfluence of the spring 57 moves forwardly with the brid-ge 56 engagingthe contacts 50 to close the electrical circuit to the heating elements23.

A modified form of our invention is shown in Fig. 4. In thismodification, the heat responsive means comprises an elongated metalplate 68 extending longitudinally across the open forwardly presentedface of the heater for sensing variations in the amount of heatreflected back to the heater by an object or objects disposed in frontof the heater. Desirably, the plate 68 is formed from a metal striphaving a high coefficient of thermoconductivity with its forwardlypresented face darkened to absorb radiant heat reflected back toward theheater. The plate 68 is secured by bolts 69 to a face plate 70 of ashielding cover 72 mounted on the adjacent faces of a pair of reflectors16 and extending the length of the heater to shield the plate 68 fromthe heating elements 23 disposed in front of the apeXes of therellectors 16. An insulating spacer sleeve 78 is disposed on each of thebolts 69 for displacing the plate 68 away from the plate 70 to insulatethe plate 68 from the cover and plate 72 and 7 0 respectively.

Desirably centered on the back face of the plate 68 is a heat responsiveswitch including a contact 79 and a switch arm 80 having a contact point81 at one of its ends normally engaging said contact for closing acircuit through wires 82 to the heating elements 23. The arm 80 issecured to the plate 68 by a heat conductive mounting block 84 adaptedto conduct heat away from the plate 68 to the arm 80 for actuating saidarm to open and close the contacts 79 and 81. Conveniently, the arm 80is a bimetallic strip comprising a metal strip 85 with a relatively lowcoecient of expansion disposed against the mounting block 84, and ametal strip 86 with a relatively high coetiicient of expansion whichcarries the contact point 81 in normally circuit-closed position againstthe contact 79. Thus, when the heater is in operation and a heatreflecting object is placed in front of the heater, the object willreflect radiant heat back toward the heater to raise the temperature ofthe plate 68. This increase in temperature will be transmitted to thearm 80 through the mounting block 84 causing the strip 86 to expand andbend the arm toward the plate 68 opening the contacts 79 and 81 to openthe circuit to the heating elements 23. When the radiant heat reected tothe plate 68 has been reduced because of the reduced output of theheating elements 23 or by removing the reflecting object, both the plate68 and the arm 80 cool, causing the strip 86 to contract and dispose thecontact point 81 in its normally closed position against the contact 79.

'By employing the thermostatic control mechanism illustrated in Fig. 4it is possible to sense variations in the amount of heat retiected backtoward the heater which can not be sensed by the control mechanism shownin Fig. 1. The elongated sensing strip 68 extending transversely acrossthe face of the heater can sense the heat reflected from a small objectdisposed in front of the heater near one end of the emitted heat beamwhich would not be reflected back to, and sensed by, the centrallypositioned thermostat 30 embodied in the heater illustrated in Fig. 5

Still another modification of our invention is shown in Figs. 5 and 6.In this modification a plurality of small thermostats 88 are mounted inthe forwardly presented face of the heater and are insulated from aradiant heat source 90 by means of any suitable shielding 92. Desirably,each of the thermostats 88 is provided with a face plate 94 adapted forabsorbing and transmitting to said thermostat heat that is reflectedback toward the heater from an object disposed in front of said heater.The several thermostats 88 and their respective contacts 95 areconnected in series by wires 96 to a relay 98 operable for actuating aswitch to open and close the circuit to the radiant heat source 90.Thus, if a heat reflecting object is positioned in front of the heaterto reflect heat back to any one of the thermostats 88, said thermostatwill be actuated to disengage its contact for actuating the relay 98 toopen the switch 160, thereby opening the circuit to the heat source 90to reduce the output of the heater and prevent igniting of therellecting object.

We claim as our invention:

l. In a radiant heater, a housing for said heater having an openforwardly presented face, a radiant heat source disposed within saidhousing, reflectors mounted rearwardly of said heat source for directingheat outwardly `from Said heater through its open face, heat responsivemeans mounted in said housing forwardly of said reectors and radiantheat source and operable for controlling the output of said heat source,and an insulating shield mounted on said reflectors for supporting saidheat responsive means in a position insulated from heat directed awayfrom said heater and disposing said heat responsive means in theforwardly presented face of said housing for actuation by heat directedback toward said heater.

2. In a radiant heater, a housing for `said heater having an openforwardly presented face, a pair of spaced radiant heating elementsdisposed within said housing, a reflector mounted behind each of saidpair of heating elements and extending forwardly therefrom for directingheat outwardly from said heater through its open face, andheat-responsive means mounted on the forward edge of the reflectors inthe forwardly presented heater face forwardly of and between said pairof heating elements, said heat-responsive means being insulated fromsaid pair of heating elements for selective actuation by heat reflectedback to said heater to control the output of said pair of heatingelements.

3. ln a radiant heater, a housing for said heater having an openforwardly presented face, a radiant heat source disposed within saidhousing, a reflector mounted rearwardly of said heat source fordirecting heat outwardly from said heater through its open face, andheat responsive means supported on the reflector forwardly of saidradiant-heat source at the open forwardly presented heater face forcontrolling the output of `said heat source, said heat responsive meansbeing insulated from said radiant-heat source for selective actuation byheat reflected back toward the heater.

4. A radiant heater as set forth in claim 3 in which said heatresponsive means comprises a heat absorbent disc adapted to be actuatedby heat reflected back toward said heater for operating a switch to openand close the circuit to said radiant-heat source.

5. A radiant heater as set forth in claim 3 in 'which said heatresponsive means comprises a bimetallic disc substantially centered inthe open face of said heater, said disc being flexed by heat reectedback toward the heater to operate a switch for opening and closing thecircuit to said radiant-heat source.

6. A radiant heater as set forth in claim 3 in which said heatresponsive means comprises a plate of heatconductive metal adapted toabsorb radiant heat reflected back to the heater for actuating abimetallic strip mounted thereon to open and close the circuit to saidheating elements.

7. A radiant heater as lset forth in claim 3 in which said heatresponsive means comprises an elongated heat conductive plate extendingacross the open face of said heater, and a bimetallic strip connected tothe rearward face of said plate, said strip being movable in response totemperature variations of said plate for opening and closing the circuitto said heating elements.

8. A radiant heater as set forth in c1airn'3 in which said heatresponsive means comprises an elongated heat conductive plate extendingtransversely across the open face of said heater, and a bimetallic stripconnected to the rearward -face of said plate at substantially thecenter thereof, said Istrip being movable in response to temperaturevariations of said plate for opening and closing the circuit to saidheating elements.

9. A radiant heater as set forth in claim 3 in which said heatresponsive means comprises a Isensing element responsive to heatreflected hack to the heater for actuating a relay controlling a switchto open and close the circuit to said heating elements.

10. A radiant heater as set forth in claim 3 in which said heatresponsive means comprises a plurality of sensing elements responsive toheat reilected back to the heater for actuating a relay for controllinga switch to open and close the circuit to said heating elements.

11. A radiant heater as set forth in claim 3 in which said heatresponsive means comprises a plurality of sensing elements responsive toheat reflected back to the heater for actuating a relay for controllinga switch to open and close the circuit to said heating elements, `saidsensing elements being connected in series to said relay for actuatingsaid relay in response to actuation of any of said sensing elements.

References Cited in the le of this patent UNITED STATES PATENTS1,652,686 Schoenfeld Dec. 13, 1927 1,704,479 Kercher et al Mar. 5, 19292,459,169 Koei Ian. 18, 1949 2,459,170 Koci Ian. 18, 1949 2,534,097Akeley Dec. 12, 1950 2,590,328 Koci Mar. 25, 1952 2,662,963 Wessel Dec.15, 1953 2,667,828 Koci Feb. 2, 1954 2,714,644 Harrison Aug, 2, 19552,753,421 Mertler July 3, 1956 2,806,421 Huck Sept. 17, 1957 FOREIGNPATENTS 440,839 Great Britain Jan. 7, 1936

